You have $1,700 for a laptop. You could pick an IBM with a 7.5-hour battery life or an HP that burns through its charge in under two hours–and they’re both great machines.

Why the disparity? The HP excels at gaming and editing video, but the requisite components chow power. Displays account for 30 to 40 percent of battery drain, and this one’s huge.

As for the CPUs, the Thinkpad’s Pentium M throttles down voltage and turns off circuitry when you’re not typing. The HP’s Pentium 4 is considerably faster, but it was designed for AC-powered desktops, and it shows. Another culprit: HP’s optical drive. Even when it’s not being used, it leaches 2 percent of the battery power; fire up a DVD, and it’ll slice life in half.

(Top left) IBM Thinkpad X40; screen size: 12.1 inches; CPU: 1.2GHz Pentium M; optical drive: none; weight: 2.7 pounds; battery life: 7.5 hours.

(Right) HP Pavilion zd7000; screen size: 17-inch widescreen; CPU: 3GHz Pentium 4; optical drive: DVD+RW/R; weight: 9.3 pounds; battery life: 2 hours